Patent GB-1147048-A (GB)
Title: Machine tool
IPC: B23Q15/00
Filed: 1966-07-13
Abstract: 1,147,048. Grinding. HEALD MACHINE CO. 13 July, 1966 [26 Aug., 1965], No. 31430/66. Heading B3D. A machine tool comprises a work support 12 and tool support 13 mounted on a base 11, a coarse feed means 22 for bringing about relative movement between the tool support and the work support, and a fine feed means for bringing about small incremental relative movement between the tool support and work support from time to time, the fine feed means consisting of a screw 33 and stepping motor 38. As described, the machine is for grinding the internal surface of a workpiece 16 by means of a grinding wheel 25. The workpiece is rotatably supported on the workhead 12 which is movable along ways 14, 15 on the base by an hydraulic motor 18. The grinding wheel 25 is carried by the wheelhead 13 which is movable along ways 19, 21 on the base by an hydraulic motor 22. A horn 26 extends downwardly from the wheelhead into a recess 27 in a block 28 slidably mounted on the base and engaged by the screw 33 which is mounted in a bearing 34 on the base and is connected by gears 35, 36 to the shaft 37 of the stepping motor 38. The front of the block carries a switch 29 which co-operates with a spindle 31, and a finger 41 on the wheelhead co-operates with a pair of switches 42, 43 on the base. A dressing diamond 23 is mounted on the workhead 12. The stepping motor (38, Fig. 2) has coils (44,..47) connected to a sequencer and driver (51) which is in circuit with a counter (58), pulser (57), logic section (63) and power supply (61). The logic section includes a count-setting circuit having two sets of selector switches and two sets of count-setting switches and the section is connected to a logic circuit which gives the sum of both sets of switches. The logic section is connected to the counter (58) which is of the binary coded decimal type including a plurality of flip-flops. The counter is connected to the sequencer and driver (51) which comprises a number of relays and flip-flops. In operation, and with a new workpiece loaded in the machine, the motor 18 is operated so that the workpiece moves and is positioned adjacent the grinding wheel 25. Motor 22 is then actuated to effect a rough grind from position a to position b as determined by the spindle 31 on the wheelhead engaging the limit switch 29 on the block, a spark-out then being effected between positions b and c. The supply to the motor 22 is then reversed to retract the grinding wheel which only returns to a position d since, during the rough grinding, a selected number of pulses have been fed to the stepping motor 38 to move the block towards the rear of the machine. The distances x and y between positions a and d correspond, respectively, to the amount to compensate for dressing of the wheel and an amount which will ensure that stress does not occur at the beginning of the finish grinding by too rapid engagement of the grinding wheel with the workpiece. At the position d, the motor 18 is actuated to move the workhead so that the dresser 23 passes over the wheel. The stepping motor 38 is then actuated to move the block 28 through the distance y so that when the motor 18 returns the workhead, the dresser is clear of the wheel. The motor 22 is thereafter actuated to rapidly feed the grinding wheel towards the workpiece but is stopped the distance y therefrom. At the same time, the stepping motor 38 is operated through a distance z to position g to engage the grinding wheel with the workpiece and effect the finish grind, the position g being determined by engagement of the spindle 31 with the switch 29. After a period for spark-out to the position a, the motor 22 retracts the grinding wheel and the motor 38 retracts the block 28 to position the grinding wheel for the next workpiece. When, after repeated dressing, the grinding wheel becomes too small, the switch 42 is actuated by finger 41 and the grinding wheel is changed. The stepping motor is then supplied with pulses at a steady rate to move the block 28 and the wheelhead to a position determined by switch 43 and the new wheel is dressed. The increment of movement of the block for each step of the motor is 0À0005 inch. All the movements of the stepping motor are controlled from the logic unit which supplies selected numbers of pulses in either direction.